In many electrical connector applications, external electrical "noise" may penetrate into the signal lines extending through the electrical connector by electromagnetic induction. Conversely, electrical noise may radiate out of the connector from the signal lines to other electrical equipment by electromagnetic radiation. Such "noise" is referred to as electromagnetic interference (EMI).
In order to eliminate or significantly reduce EMI, electrical connectors often are provided with a shield which surrounds the electrical connector at least about the signal line termination area thereof. A typical shield is a metal shell which often is stamped and formed of sheet metal material. The metal shell provides a covering about the outer periphery of an insulative housing in which a plurality of terminals are mounted. For instance, the sheet metal shell may be in the form of a quadrangular tube shaped configuration, with a front opening to expose a front mating end of the housing, and a rear opening from which tail portions of the terminals extend. Most often, the sheet metal shell has opposed ends forming a joint, and the opposed ends often are overlapped at the joint.
One of the problems in simply overlapping opposed ends of a metal shell to form a joint, is that a gap often is formed between the opposed ends. The gap not only allows for EMI leakage, but the gap allows for penetration of environmental gases and/or dust to enter the connector. If the connector is to be mounted on a printed circuit board, soldering processes often are used, and the heat involved in such processes causes thermal expansion of the metal shell, which results in a widening of the gap between the opposed ends at the joint.
In order to prevent the opposed ends of the shell from widening at the joint, the opposed ends may be fixed, as by spot welding. Unfortunately, this inherently requires an additional processing step which significantly increases the cost of the connector.
Another problem with metal shells which have opposed ends that overlap at a joint, is that the overlapped ends increase the thickness of the shell at the joint. In other words, two overlapped ends double the thickness of the metal shell to create a bulged portion which is undesirable in many applications. For instance, the joint in a sheet metal shell typically is located at the bottom of the connector. If the connector is to be surface mounted on a printed circuit board, the bulged joint creates an uneven surface and prevents the bottom of the connector from being coplanar with the surface of the circuit board.
The present invention is directed to solving the various problems identified above by providing a joint between the opposed ends of a metal shell which is the same thickness as the metal material forming the shell and which fixes the joint without extraneous processing such as welding.